Production of alkyl substituted aryl hydrocarbons



Patented Mar. 26, 1935 UNITED STATES PATENT OFFICE PRODUCTION OF ALKYL SUBSTITUTED ARYL-HYDROCARBONS No Drawing. Application August 28, 1933, Serial No. 687.247

2Claims.

The present invention relates to the alkylation of aryl hydrocarbons by the substitution of alkyl radicals of relatively high carbon content for nuclear hydrogen of such hydrocarbons. It is more particularly concerned with the production of alkyl substituted aryl hydrocarbons having from eight to thirty carbon atoms in the alkyl side chain. It is the object of the invention to produce compounds of this type by a commercially feasible process affording a high yield of the desired compound by a relatively inexpensive procedure. Important economies are attained in the performance of the process by reason of the fact thatit requires the use of only a relatively small amount of material as a catalyst and because of the fact that the unreacted products are recovered in a form which makes possible their reuse in a repetition of the process. The process of the invention is based fundamentally upon the well-known Friedel and Crafts reaction by which alkyl chlorides are condensed with substituted or unsubstituted aryl hydrocarbons in the presence of anhydrous aluminum chloride or other equivalent catalyst and upon the wellknown synthesis by which oleflns are condensed with aryl compounds in the presence of a catalyst to produce the corresponding alkyl derivatives of the aryl compounds used in the condensation reaction. It involves the initial step of chlorinating paraiiin hydrocarbon material of the desired carbon content or range and the subsequent utilization of the chlorinated hydrocarbon material so produced in the production of the desired derivative of an aryl compound.

A number of diiliculties are encountered in connection with attempts to perform such a series of operations in the performance of the Friedel and Crafts reaction in connection with the production of alkyl chlorides of high molecular weight and the subsequent separation of monochlorides so formed from unreacted paraffin hydrocarbons and poly-chlorides.

The practice of the chlorination operation by a procedure involving the conversion of the major portion of the hydrocarbon into chlorides necessarily results in the production of a large proportion of undesired polychlorides. Even in cases in which chlorination is terminated long before a molecular proportion of chlorine has combined with the hydrocarbon, a great deal of undesired formation of polychloride material occurs when the chlorination reaction takes place in metal apparatus or other apparatus tending to catalyze the splitting of the monochlorides formed to produce oleflns and hydrochloric acid,

as olefins so formed have a tendency to promptly combine with more chlorine to produce undesired dichlorides. If the chlorination operation is not carried to substantial completion, serious problems of distillation are also encountered in separation of unreacted paraflin hydrocarbons from chlorides preparatory to the subsequent step in which the chlorides are condensed with the aryl hydrocarbon.

The higher molecular weight chlorides which are to be used in the condensation reaction are so close in boiling range to the hydrocarbons from which they are derived that they can only be separated from the unreacted hydrocarbons with great difliculty. In some instances of chlorinationmf mixtures of isomeric hydrocarbons these ranges actually overlap each other and in such instances eflicient separation is extremely difficult. A further difficulty is encountered by reason of the fact that a large proportion of these alkyl chlorides are decomposed when they are heated in metal apparatus. Attempts at chlorination or distillation in such apparatus thus result in undesirable splitting of much of the chlorinated material to produce olefins and hydrochloric acid. Chlorination in metal apparatus is especially undesirable, as the oleflns formed by decomposition of chlorides in such apparatus promptly tend to recombine with chlorine to produce dichlorides. Large amounts of catalysts are also required in connection with condensation of alkyl chlorides with aryl hydrocarbons, and another important feature of the present invention resides in the development of a process in which only relatively small amounts of catalysts are required.

In the practice of the present invention the paraflin hydrocarbon material is first chlorinated to produce a mixture of hydrocarbons and chlorides. The chlorination of the hydrocarbon may be performed by passing gaseous chlorine into a. mass of liquid hydrocarbon and this chlorination-operation is discontinued long before a stage is reached involving combination of a molecular equivalent of chlorine with the hydrocarbon under treatment. This chlorination operation is preferably conducted in glass or other non-metallic apparatus in order that decomposition of chlorides at this stage and subsequent formation of polychlorides by recombination of olefins so formed may be substantially completely avoided.

At the conclusion of the operation in which the hydrocarbon material is partially chlorinated, a small amount of a catalyst adapted to cause splitting of alkyl chlorides to form oleflns and hydrochloric acid is added to the entire mass of mixed chlorides and paraffin hydrocarbon. A small amount of ferric chloride may be used for this purpose. the material being refluxed together with the splitting catalyst for a period sufficient to effect splitting of the major portion oi!- the alkyl chlorides. The mixture is then cooled and mixed with the aryl hydrocarbon with which it is to be condensed. It is to be noted that no attempt at separation of parailin hydrocarbons from chlorides and oleflns is made prior to this operation.

The mixture of aryl hydrocarbon, alkyl hydrocarbons, olefins and unsplit alkyl chlorides is next stirred din-ing the addition of a sufficient additional quantity of catalyst to eifect the condensation of the alkyl chlorides and olefins with the aryl hydrocarbon. The mixture is heated to facilitate reaction and stirring is continued until the reaction is completed. The complex formed by the condensation reaction may then be decomposed by the addition of water and distilled until the unused hydrocarbon is recovered. The residue is then further distilled to effect separation of the desired alkyl substituted aryl hydrocarbon from the residue.

In a typical example of the practice of the invention, the following procedure was adopted:

1000 gms. of mixed parafiln hydrocarbon material consisting principally of do-decane was partially chlorinated by bubbling chlorine through the material until it had gained 70 gms. in weight; i. e. until approximately 35% of the hydrocarbons had been converted to monochlorides. The chlorides of the mixture were then partially decomposed by refluxing the entire mixture with 5 gms. of ferric chloride for one hour. The mixture was then cooled and poured into 3 liters of benzene and stirred during the addition of 75 gms. of aluminum chloride. This mixture was then warmed to C. and maintained at that temperature during continued stirring for a period of 15 minutes. Water was then added to the mixture to effect decomposition of the complex and the mixture steam distilled to recover benzene. The residue was then vacuum distilled and yielded 636 grams of saturated hydrocarbon material of the same carbon content as that used in the original chlorination operation. No olefin was recovered in connection with this distillation and it therefore appeared that all of the olefin in the crude mixture was condensed with benzene. The residue from the aforementioned distillation was next subjected to further vacuum distillation and yielded 220 grams of material having a boiling range from 185-210 C. and comprising principally lauryl benzene.

It is to be noted that the practice of the invention in accordance with the above procedure involves avoidance of the' loss of valuable hydrocarbon and other difiiculties incident to the formation of dichloridcs such as would be encountered in connection with attempts to sheet more complete chlorination of the hydrocarbon mixture and that the use of the entire mixture of chlorides and parafiin hydrocarbons in the subsequent steps of splitting and condensation ob-- viates the diflicult problems of fractionation referred to above. While great difficulty would be encountered in attempts to separate the unreacted parailin hydrocarbon material from corresponding chlorides the separation of this maicrial from the alkyl substituted aryl compounds in accordance with the present invention by distillation is not difficult, as these last mentioned compounds have boiling ranges much higher than the paraiilns or chlorides used in the condensation reaction. It will be further noted that the conversion of a large proportion of the alhl chlorides to olefins by splitting enables us to effect a substantial saving in connection with the cost of the catalyst used in the condensation reaction, as the condensation of olefins with aryl hydrocarbons is a more truly catalytic reaction and does not, therefore, require the use of the large quantities of catalytic material necessary to the production of a comparable quantity of the desired derivative by the direct performance of a Friedel and Crafts reaction with respect to the necessary quantities of alkyl chloride and aryl hydrocarbon. The applicant is thus enabled to eiicct a substantial economy over prior methods involving difficult and expensive attempts at distillation of paraflln hydrocarbons from corresponding chlorides and the condensation of these chlorides directly with aryl hydrocarbons to produce the desired alkyl derivatives.

Modifications will be obvious to those skilled intheart,andIdonot,therefore, wishtobelimited except by the scope of my subjoined claims. The chlorination may, for example, be carried out in the vapor phase provided a substantial molecular excess of hydrocarbon is used. In the interpretation of the claims, I wish it to be understood that the term aryl compound is intended to include not only unsubstituted aryl hydrocarbons, such as benzene and naphthalene, but also such unsubstituted derivatives of these compounds as are capable of condensation with alhl chlorides in accordance with the Friedel and Crafts reaction, or with the corresponding olefins.

What I claim is:

1. The method of producing an alkyl derivative of an aryl compound which comprises partially chlorinating parailin hydrocarbon material corresponding in carbon content to the alkyl radical of the desired derivative to produce a mixture of the paraiiin hydrocarbon and the corresponding alkyl chloride, subjecting the mixture, including chlorinated material and unreacted paraflin hydrocarbon to a splitting reaction adapted to convert alkyl chlorides to olefin and hydrochloric acid, mixing the mass of material so formed with the aryl compound adapted to constitute the nucleus of the desired derivative, condensing the alkyl chloride and olefin of the mixture with the aryl compound and thereafter separating unreacted parailln hydrocarbon from the reaction mixture by fractional distillation.

2. The method of producing an eight to thirty carbon atom alkyl derivative of an aryl compound which comprises partially chlorinating parafiln hydrocarbon material corresponding in carbon content to the alhl radical of the desired derivative to produce a mixture of the parafiin hydrocarbon and the corresponding alkyl chloride, subjecting the mixture, including chlorinated material and unreacted paraflln hydrocarbon to a splitting reaction adapted to convert alkyl chlorides to olefin and hydrochloric acid, mixing the mass of material so formed with the aryl compound adapted to constitute the nucleus of the desired derivative, condensing the alkyl chloride and olefin of the mixture with the aryl compound and thereafter separating unreacted paraflin hydrocarbon from the reaction mixture by fractional distillation.

CHARLES A. THOMAS. 

